Abstract: A lighting control apparatus to provide variable intensity light from high pressure discharge lamps using two high pressure discharge lamp loads connected in series to provide more widely variable intensity of light. The outputs of two ballasts may be connected in series to feed the series connected discharge lamp load. Preferably a feedback signal proportional to load current is used to stabilize operation. In addition, circuitry is preferably provided to maintain a predetermined minimum current to prevent extinguishing of the lamps from low current and "hot restrike" circuitry is provided to limit the maximum load voltage when the lamps are extinguished.

Abstract: Lighting control apparatus for controlling the light intensity of high-intensity-discharge (HID) lamps operated from an AC source while eliminating the tendency for such lamps to extinguish during the dimming thereof. The apparatus comprises a variable reactive ballast controlled with respect to its reactance by a solid-state switching device which is responsive to a timed control signal provided by a signal generating device operating from the same AC source. A lamp voltage sensing device develops a feedback signal which varies in accordance with the voltage drop across the lamps being ballasted. A signal sensing and overriding device combines the feedback signal and the timed controlled signal and causes the feedback signal to override the timed control signal before the lamp voltage reaches such value as might cause the lamp to extinguish.

Abstract: High-intensity arc-discharge (HID) device of the metal-halide additive type incorporates as essential discharge-sustaining constituents mercury and inert ionizable starting gas and also sodium and/or lithium iodides and/or bromides as well as scandium iodide and/or bromide. The molar ratio of alkali metal halide to scandium halide is from about 1.7:1 to about 5:1 and this greatly enhances the device efficacy for the generation of visible light, which can be enhanced by as much as 32 percent.

Abstract: An arrangement to eliminate the initial current overshoot which normally occurs when a tungsten incandescent lamp is connected to a power source. The arrangement uses a negative temperature coefficient thermistor having a certain predetermined mass. It has been determined that a practical limiter to eliminate current overshoot can be made only when the mass of the limiter is within a relatively narrow range. The hot and cold resistance of the limiter must also be within prescribed ranges to give a limiter which is not only effective in eliminating the current overshoot, but also efficient in steady state operation such that the limiter dissipates less than 1% of the total power.

Abstract: To improve the performance of fluorescent lamps which use strontium chloroapatite activated by a divalent europium as a luminescent material, prior to coating onto the lamp envelope, the luminescent material is washed with an aqueous fluoride solution and then rinsed to remove residual soluble fluoride.

Abstract: Incandescent source of visible radiations comprises a refractory support member having a thin, refractory material layer thereover, with both the support and the thin layer adapted to be heated to high temperatures. The material comprising the thin layer is highly absorptive for visible radiations and thus is a correspondingly good emitter for such visible radiations, and the material comprising the thin layer is highly transmissive for infrared radiations and a correspondingly poor emitter for such infrared radiations. Minute optical discontinuities in the thin layer act to scatter infrared radiations and the infrared radiations which are generated in the support member are scattered back to the support member in order to contribute to the heating of same. Visible radiations, in contrast, are absorbed and emitted by the thin layer so that this layer is a very selective radiator.

Abstract: Dissolved molybdenum is recovered from spent sulfuric acid-nitric acid solution by adding ammonium hydroxide to spent acid solution to raise pH thereof to from about 1.5 to about 3, and preferably from 2 to 3. Solution is then agitated and simultaneously heated at a temperature less than about 95.degree.C until substantially all dissolved molybdenum is precipitated as ammonium molybdate complex, from which the precipitate is then recovered.

Abstract: A device to generate light of a quality which will accent the mismatch in color appearance of objects having different spectral reflectance curves but which appear at least generally similar in color and lightness under illumination by daylight. As there are many objects which match under one illuminant such as daylight, but do not match under other illuminants, there are many applications in which it is desirable to provide for early detection of potential mismatches. This invention generates visible radiation substantially confined to at least two of the 405-435 nm, 475-505 nm, 565-595 nm, and 645-675 nm wavelength ranges, and which preferably has less than 20 percent of the radiations in the 435-465 nm, 525-555 nm and 595-625 nm wavelength ranges.

Abstract: Outdoor lighting fixture utilizes lamp ballast which includes both solid-state control circuitry and a relatively massive inductor ballast. The solid-state control circuitry is mounted in a separate housing, such as the photocontrol housing, which is affixed to the exterior of the fixture by means of a plug-type receptacle, and the relatively massive inductor portion of the ballast is contained within the fixture body. Those portions of the solid-state control circuitry which require cooling use the separate housing as a heat sink. If troubles are encountered in the solid-state circuitry, the entire circuit can be replaced simply by plugging in a new unit.